1. Field of the Invention
The present invention relates to a die bonding apparatus and, more particularly, to a die bonding apparatus for bonding a large number of separate semiconductor chips (hereinafter referred to as dice) of a semiconductor wafer to works such as lead frames.
2. Description of the Related Art
A conventional die bonding apparatus of the above-described type will be described below with reference to FIG. 9. A die pick-up station 2 for picking up a separate die of a wafer is connected to a wafer loader/unloader 1 which accommodates a plurality of semiconductor wafers (not shown). A die position correcting station 3 for correcting the position of a die is connected to the die pick-up station 2. A bonding agent supply station 5 for supplying to a work a bonding agent such as a solder or a resin adhesive is connected to a work loader 4 which accommodates a plurality of works (not shown) such as lead frames or ceramic substrates which serve as die mounting media. A die bonding station 6 for bonding a die to a work is coupled to the bonding agent supply station 5. The die pick-up station 2 is connected to the die bonding station 6 directly or via the die position correcting station 3 so as to supply a die to the bonding station 6 from the die pick-up station 2, and a work unloader 7 for accommodating works with the die bonded thereto is connected to the bonding station 6.
In the above-described die bonding apparatus, die bonding is conducted in the manner described below.
First, one semiconductor wafer is fed from the wafer loader/unloader 1 to the die pick-up station 2. The wafer has a large number of dice separated from each other and has been subjected to a wafer test or a die sorting test in which a bad mark is appended to a defective die. In the die pick-up station 2, one good die which has no bad mark appended thereto is picked up from the wafer which has been supplied from the wafer loader/unloader 1, and is supplied to the bonding station 6 directly via a route a shown in FIG. 9. Alternatively, the die which has been picked up in the die pick-up station 2 is fed via a route b to the die position correcting station 3, where the angular position of the die is corrected, and it is then supplied to the bonding station 6 via a route c.
On the other hand, in the bonding agent supply station 5, a bonding agent is supplied to a work which has been fed from the work loader 4 at a predetermined position, and this work is then fed to the bonding station 6.
In the bonding station 6, the die which has been fed from the die pick-up station 2 directly or via the die position correcting station 3 is bonded to the work which has been conveyed from the bonding agent supply station 5.
After the bonding of one die has been completed, a next good die is supplied from the die pick-up station 2 to the bonding station 6 so as to be bonded to another work. The works with the dice bonded thereto are accommodated in the work unloader 7.
Bonding is performed on successive dice in the manner described above until all the good dice have been picked up from the semiconductor wafer which has been supplied from the wafer loader/unloader 1 to the die pick-up station 2. When all the good dice have been picked up, the wafer loader/unloader 1 retrieves this wafer from the die pick-up station 2, and supplies a new wafer to the die pick-up station 2. The die bonding operation begins again using this new wafer.
However, in the conventional apparatus, no die can be supplied to the die bonding station 6 while the wafer loader/unloader 1 is replacing a semiconductor wafer, and the bonding operation therefore has to be interrupted during this time, resulting in a reduction of the bonding capacity per unit time.
In particular, when a wafer of the type with a low yield due to an increase in the dimensions of a die or higher integration having a reduced number of good dice per wafer, bonding capacity per unit time becomes greatly reduced, as shown by the solid line in FIG. 10, since the ratio of the wafer replacing time to the overall operating time of the die bonding apparatus is high.